Conventionally, it is known that during large-scale diastrophism such as an earthquake, a volcanic eruption or the like, compressive force between stratum and/or a pressure of magma are gradually increased, so that a piezoelectric effect occurs due to a highly increased pressure in a crust immediately before occurrence of the earthquake or volcanic eruption, or a strong electromagnetic wave, heavy earth current, strong electrostatic action or the like occurs due to a chemical phenomenon, an electrokinetic phenomenon or the like.
Under such a circumstance, various means such as measurement of distortion/deformation of a crust, detection of a variation in electromagnetic wave/earth current generated from a crust as a symptom of an earthquake and the like are attempted in order to predict occurrence of an earthquake.
With regard to an electromagnetic wave emitted from a crust, it is known that an electromagnetic wave and an earth current are discharged from a region near a seismic center or hypocenter due to a compressive pressure and/or a frictional pressure abnormally increased near a place of a dislocation and due to exo-electrons generated by breakage of a base rock.
As a method for detecting a variation in electromagnetic wave or magnetic force line to predict an earthquake, it is proposed that a cloud chamber having transpired gas such as ether or the like encapsulated therein is arranged in an artificial satellite to visually observe or photograph a portion of the gas linearly whitened due to passage of an electromagnetic wave (corpuscular ray) or a magnetic force line discharged from an interior of the ground therethrough (Japanese Patent Application Laid-Open Publication No. 133174/1979, Japanese Patent Application Laid-Open Publication No. 103388/1979 and Japanese Patent Application Laid-Open Publication No. 13802/1980).
Also, it is proposed that a plurality of electrodes are embedded in the ground to electrically detect a specific variation in earth current immediately before an earthquake, to thereby predict occurrence of the earthquake (Japanese Patent Application Laid-Open Publication No. 37580/1983).
The former method proposed is carried out by visual observation or photograph observation, to thereby cause many mistakes and errors in judgment of a direction of a hypocenter, a scale of an earthquake and the like and lack objectivity. Also, it has another disadvantage of failing in discrimination between prediction of actual occurrence of an earthquake and malfunction of the device due to affection of various noise electromagnetic waves depending on an environment in which the device is arranged. In particular, it fails to exhibit satisfactory utility in modern cities or towns in which large-sized engines for airplanes, vehicles and the like are driven and electric machines and electronic equipments are crowded, environs thereof, industrial areas and the like.
Also, the above-described method of mounting the electromagnetic sensor in the artificial satellite substantially fails to specify a position of occurrence of diastrophism, a scale thereof and time thereof because the satellite is excessively remote from diastrophism, even when the sensor has a capability of capturing an electromagnetic wave. Also, it causes an excessive increase in cost for launching of the satellite and cost for control, communication and maintenance, to thereby lack utility from an economical point of view.
Further, the latter method proposed is adapted to carry out electrical detection and electronic information processing, to thereby be superior in objectivity to the former method. Nevertheless, it likewise causes undesired introduction of many complicated noises into the electrodes in modern cities or towns in which a number of electrodes for equipments consuming a large amount of electric power are embedded, environs thereof, industrial areas and the like, to thereby substantially fail in judgment, resulting in failing to be put to practical use.
The inventor has carried out an astronomical observation for many years in his own astronomical observatory. In particular, he has continuously carried out a meteor observation using a VHF radio wave generated from an FM broadcasting station remote sufficiently to cause a failure in receiving of a direct wave, wherein an abnormal reflection phenomenon of a VHF radio wave (abnormal propagation of a VHF radio wave (frequency modulation or the like)) due to formation of an ionospheric column in the upper atmosphere owing to inrush of meteor into the atmosphere is observed or an FM broadcasting radio wave in which abnormal propagation occurred is received to analyze data thereon, to thereby observe the meteor.
In the course of the meteor observation, the inventor found a continuous abnormal propagation phenomenon continuing over several hours to three days and, in a long case, four to six days rather than a temporary VHF abnormal propagation phenomenon as short as less than one second due to meteor inrush and, as a result, took notice of relationship between the abnormal receive data and occurrence of diastrophism such as an earthquake or the like.
The inventor made analysis and research of data on an abnormal propagation phenomenon of a VHF radio wave and earthquake information before and after occurrence of the phenomenon over about two years. As a result, it was proved that occurrence of the abnormal propagation phenomenon fully coincides with information of an earthquake occurring between the FM broadcasting station and a receiving point and properties of the receive data are fully correlated to a scale of the earthquake, as well as formation and extinguishing thereof.